1. Field of the Invention
The present invention relates to a semiconductor integrated circuit (system LSI) incorporating therein a plurality of functional blocks and particularly relates to a semiconductor integrated circuit capable of validating or invalidating a plurality of functional blocks.
2. Description of the Related Art
In recent years, as circuits are increasingly made smaller in size or larger scaled, it becomes a mainstream in circuit design to use functional blocks.
As for functional blocks, when semiconductor integrated circuits are developed, not only internal functional blocks which can be freely used but also external functional blocks which require royalties are increasingly introduced.
With reference to FIG. 8, a semiconductor integrated circuit employing conventional functional blocks will be described. Reference numeral 7 denotes a semiconductor integrated circuit. The semiconductor integrated circuit 7 is comprised of a central processing unit (CPU) 1, a memory 2 for storing programs, a peripheral circuit 3, an internal functional block 4 held inside the circuit and freely usable, and external functional blocks 5 and 6 introduced from externally and requiring royalties.
The specification of the semiconductor integrated circuit 7 is determined in advance. The semiconductor integrated circuit 7 incorporates therein the necessary external functional blocks 5 and 6 depending on the specification of the circuit 7.
Necessary external functional blocks differ depending on each user. Accordingly, semiconductor integrated circuits 7 incorporating therein different external functional blocks are developed and manufactured, respectively.
That is, on the one hand, semiconductor integrated circuits each incorporating therein only the external functional block 5 are developed and manufactured independently.
On the other hand, semiconductor integrated circuits each incorporating therein only the external functional block 6 are developed and manufactured independently of the former semiconductor integrated circuits.
In some cases, semiconductor integrated circuits each incorporating therein both of the external functional blocks 5 and 6 are developed and manufactured.
In other words, various types of semiconductor integrated circuits are developed and manufactured.
In case of the conventional integrated circuits as stated above, it is necessary to develop and manufacture semiconductor integrated circuits having a plurality of types of specifications and different numbers of external functional blocks independent from one another.
For example, if a specification including both of the external functional blocks 5 and 6 is standard and a certain system does not require either one of the external functional blocks, it has been necessary to develop and manufacture a different semiconductor integrated circuit, or a semiconductor integrated circuit incorporating therein the unnecessary external functional block is manufactured and a user is charged for a royalty on the unnecessary external functional block.
As can be seen, it has been conventionally difficult to sufficiently satisfy both of the requirements of ensuring the versatility of semiconductor integrated circuits and optimizing royalty payments.
It is, therefore, a main object of the present invention to provide a semiconductor integrated circuit capable of ensuring the enhancement of versatility and the optimization of royalties.
The other objects, features and advantages of the present invention will be readily apparent from the description which follows.
A semiconductor integrated circuit according to the present invention comprises: one or a plurality of external functional blocks; switching means having a logical content as to whether to validate or invalidate each external functional block; and validating and invalidating means for validating or invalidating an input and an output to each external functional block in accordance with the logical content of the switching means.
According to the present invention, the validating and invalidating means can validate or invalidate the input and the output to each external functional block according to the logical content of the switching means.
Therefore, if a semiconductor integrated circuit manufacturer incorporates one or a plurality of external functional blocks in the semiconductor integrated circuit, a user can deal with a necessary external functional block by validating the use of the block and deal with an unnecessary external functional block by invalidating the use of the block.
As a result, if royalties on external functional blocks are charged, the user is charged the royalty on the external functional block set valid but not charged the royalty on the external functional block set invalid.
Consequently, the present invention can provide a semiconductor integrated circuit satisfying both a requirement to enhance versatility and to optimize royalty payment.
It is noted that the presence or absence of royalties is not necessarily essential in the present invention. If royalty payment is obligatory on users, the present invention can properly deal with it.
According to the present invention, the switching means preferably includes a memory for storing the logical content as to whether to validate or invalidate the input and the output to each external functional block.
According to the present invention, the memory is preferably a nonvolatile memory.
According to the present invention, the validating and invalidating means preferably includes a logical circuit for invalidating the input and the output to each external functional block if the logical content of the switching means is a content of invalidating the input and the output to each external functional block.
According to the present invention, the logical circuit preferably includes an AND gate for obtaining a logical product of the logical content and an input signal, and inputting the logical product into each external functional block.